Apparatus for catalytic cracking



Oct. 13, 1942'. L c. RUBIN ErAL 2,298,593

APPARATUS FOR CATALYTLC GRAGKING Filed NQv. 12, 1938 2 Sheets-Sheet 1of.13,l1942. L; c. Rum am i 2,298,593

APARATUS FOR CATALYTIC CRACKING Filed Nov. 12,-1958 2 'sheets-sheet 2iw: I

l l I I I l l l I i I I l l l I 1,/ l w l l l [l] l 7 f; I I H, l i /1 ll' Tl II III ATTOR EY Patented Oct. 13, `1942 APPARATUS FOR CATALYTICCBACKIN G Louis C. Rubin, West Caldwell, Walter B. Montgomery, Summitand William J. Degnen,

Cranford, N. J., assignors to The M. W. Kellogg Company, New York, N.Y., a corporation oi' Delaware Application November 12, 1938, Serial No.240,100

1 Claim.

4Our invention relates to a method and apparatus for catalytic crackingand more particularly to an improved method for cracking with the aid ofa catalyst which is continuously supplied to the reactants andcontinuously removed from the reaction zone.

It has been suggested, in the practice of catalytic cracking, to flowcatalyst'material in iinely divided form through the catalyst chamber incontact with the reactant so that the catalyst material in a constantstate of activity will be continuously supplied, thus enabling a closercontrol over the desired products to be exercised and a higher yield tobe obtained.

In the suggestions of the prior art, the catalyst was made to ilowcountercurrent to the re-l actants. We have discovered that, whencountercurrent flow of catalyticmaterial to the reactants is practiced,the hydrocarbons produced, as for example, gasoline, pass progressivelythrough more active`catalysts. We have found that, when the nascent lowboiling hydrocarbons resulting from catalytic cracking thus come incontact with a more active catalyst. they are in part destroyed. Thisresults in an increased dry gas yield and a decreased gasoline yield inthe case of cracking heavy hydrocarbons to light hydrocarbons suitablefor use as a motor fuel. We have discovered, too, particularly at highvelocities of vapor flow, that incountercurrent ilow static catalyst mayexist or that the catalyst iiow is reversed, thus reducing the benefitsob. tained from the use of a continuously moving catalyst.

One object of our invention is to provide a novel methodvoi catalyticcracking employing a moving catalyst.

Another object of our invention 'is to provide a novel apparatus capableof carrying out the method of our invention.

Other and further objects o! our invention will appear from thefollowing description.

In the accompanying drawings which form part of the instantspecification and are to be read in conjunction therewith and in whichlike reference numerals-are used 'to represent like parts in the variousviews,

Figure 1 is a schematic view of apparatus capable of carrying out themethod of our invention.

Figure 2 is a sectional view of a catalytic cracking chamber formingpart of the apparatus of our invention and capable of carrying out themethod of our invention.

Figure 3 is a fragmentary sectional view taken on a line 3-3 of Figure2.

Figure 4 is an enlarged fragmentary view of a detail showing thedischarge end of the reaction tubes.

Figure 5 is a sectional view taken'on a line 5-5 of Figure 4.

Figure 6 is a sectional view on an enlarged scale, taken on a line 6 6of Figure 4.

Figure 7 is a fragmentary view on an enlarged scale of a modied form ofa catalyst discharge assembly enabling' a more accurate control of thecatalyst ilow to be exercised.

Figure 8 is a sectional view taken on a line 8-8 of Figure 7.

In general, our invention contemplates a method of catalytic cracking inwhich the hydrocarbon vapors to be cracked, are passed through tubescontaining a cracking catalyst concurrently with a catalyst material iniinely divided form. Concurrent iiow enables us to exercise a vmoreaccurate control of the catalyst flow, decreases the amount of staticcatalyst to a minimum, decreases the dry gas yield and increases theyield of desired hydrocarbons. Furthermore, we have found that incatalytic cracking with concurrent ow of catalyst, the octane number ishigher when cracking to gasoline-like hydrocarbons. In cracking to formDiesel fuel, the maximumpour point was decreased from about 10 to below35 F.

Any suitable cracking catalyst may be employed. We prefer to use afinely divided silica catalyst-on which there has been hydrolyticallyadsorbed a small amount of aluminum oxide.

More particularly referring now to the drawings, the hydrocarbons to becracked may be of any suitable type and are taken from a storage tank Ithrough line 2 and pumped by pump 3 through pipe 4 through the coils 6and 'I of a furnace 8 in which fuel, such as gas from a gas main 9, isburned in burners I0 to heat the oil to the desired crackingtemperature, which may be anywhere between 800 F. and 950 F. or higher.The heated oil is withdrawn from the furnace 8 through pipe Ilcontrolled by valve I2` and passed into an evaporator I3 in which theoil is separated into vapors and unvaporizod oil. The unvaporized oil iswithdrawn from tho evaporator through pipe I4 and pumped by pump I5through a heat exchanger I6 which is supiiow through pipe I8 into thebottom of' the evaporator i3 to control the bottom temperature lthereof. The remainder of the unvaporized oil is withdrawn from theprocess -through pipe 28. The vapors withdrawn from the top of theevaporating zone |3 through pipe 2| are at the desired crackingtemperature. If desired, they may be superheated by any suitable means(not shown). Fresh, nely divided catalyst from any suitable source ispassed into a hopper 22 by a conveyor 23 for passage through crackingreac' tion tubes housed within the reaction chamber 24 and shown indetail in Figure 2. The arrangement is such that the hot vapors, atcracking temperature, now downwardly through the reaction tubes with thecatalyst at a rate sumcient to provide a time interval in which thedesired cracking reaction may take place. 'Inthe temperature of thevapors during their passage through the reaction zone is maintained bymeans of heat exchange. Gas is supplied from the gas main through pipe28 past valve 26 to a burner 21 in which hot gases of combustion aregenerated. The hot gases of combustion pass through a conduit 28 into ajacket 28 in heat exchange with the reaction tubes. The exhaust gasesare withdrawn from the hot Jacket through duct 30. The larger portionthereof pass chamber 3| for passage through duct 32 to a ilue.

A portion of the spent gases is taken by blower 33 past control damper34 for passage through duct 35 for admixture with the freshly generatedhot gases of combustion. The admixing of the spent gases with the hotgases enables a control of the temperature of the resultant mixture tobe exercised. It is contemplated as well to pass the heating mediumthrough the vjacket in a coimtercurrent direction to the reactant vaporsand catalyst, introducing the medium around the lower ends oi' thecatalyst tubes in the location of the pipe 38 and discharging theheating medium through pipe 28. The cracked vapors are separated fromthe spent catalytic material and withdrawn from the reaction chamberthrough pipe 38 and introduced into a fractionating tower 31 which maybeof any suitable type, as for example, one equipped with bubble trays 38.r.Reflux condensate is withdrawn from the bottom of the fractionatingtower 81 through pipe 38 and pumped by pump 48 through heat exchanger 4|which is supplied with a cooling medium through pipe 42. Cycle stock iswithdrawn from the heat exchanger through pipe 43, controlled by valve44. Control reflux is passed t the fractionating tower through pipe 48,controlled by valve 48. The cracked vapors and fixed gases are removedoverhead through pipe 41 and passed through a condenser 4'8, which issupplied with a cooling medium through pipe 49. The condensate iswithdrawn from the condenser through pipe I8 and passed into a separatorIl from which the fixed gases are withdrawn through pipe 82 controlledby back pressure controlled valve 83, for passage to the fuel gas mainI4.

Gasoline is withdrawn from the separator 8| through pipe 8l and pumpedby pump 88 through pipe 81 to storage. A portion of the gasoline passesthrough pipe 58 controlled by valve 58 for introduction to the top ofthe fractionating tower 31 as a lcontrol reux to control the top towertemperature. The spent catalyst passes into the catalyst dischargehoppers 88 from which asmuch as cracking is an endothermic reaction,

.catalyst tubes is determined.

it is withdrawn through duct 8| for introduction .to a conveyor 82 forpassage to a catalyst retroduced from a sealing fluid main 68 through`pipes 61 and 88. Sealing gas is controlled by control valves 69 and 10.The control valves are diaphragm valves controlled by the differentialpressure existing within the reaction cham,- ber and in the sealinghoppers. The pressure in the hopper 22 is communicated through pipe 1|,the pressure within the reaction chamber being communicated through pipe12. The arrangement is such that the pressure within the hopper 22 ismaintained above that existing within the reaction chamber. A similararrangement operates the valve 69 at the discharge side of the reactionchamber.

Referring now to Figure 2, the flow of the catalyst is controlled by a,valve 13, the catalyst passing into an upper chamber 14 formed withinthe reaction chamber 24 by a tube sheet 15 which acts as a distributingplate to distribute the catalyst 16 to the feeder tubes 11. Thearrangement is such that accumulations of stagnant catalyst adjacent theupper openings of the catalyst tubes 18 is avoided. The feeder tubes 11extend some distance downwardly into the reaction tubes 18. Below thefeeder tube sheet 15 we position a tube sheet 19 in which the catalysttubes 18 are welded or rolled. The space 88 between the tube sheet 15and the tube sheet 18 serves as an inlet vapor space to which theincoming hot; vapors to be cracked are introduced through pipe 2|. Thefeeder tubes 11 feed the catalyst to the catalyst tubes 18. The lengthof the feeder tubes will determine the height of the catalyst materialmaintained within the catalyst tubes. By varying the length of thefeeder tubes, the amount of catalyst in the 'I'his enables us to changethe amount of catalyst forcraoking various types of stock .and employingdifferent types of catalytic material.

'I'he lower portions of the catalyst tubes are welded or rolled in alower tube sheet 8|. A plurality of baiiies 82 and 83 are disposedaround the exterior oi' catalyst tubes 18 transversely of the heatingjacket 23 to direct the flow of heating medium which is introduced tothe heating Jacket through duct 28 and withdrawn therefrom through duct38. Heat exchange between the heating medium and the reactants withinthe catalyst tubes supplies heat to the endothermic cracking reaction.

In order to remove the catalyst and the vapors separately from the lowerends of the catalyst tubes, we provide means to effect the separation ofthe catalyst and the vapors. It will be noted that the catalyst tubes 18extendI beyond the lower tube sheet 8|. To these extensions are fittedelements comprising upper cylindrical portions 84 and lower conicalportions 85. The cylindrical portions 84 are provided with slots 88,normally covered by screens 8.1. The screens are made with a meshsuiliciently small to permit the discharge of the vapors whilepreventing the catalyst from passing therethrough.

The tube ends are arranged in rows corresponding with the catalyst tubesto which they are itted. To facilitate the placing or fitting of thetube ends on the tubes, they are secured to structural members such asangles 88. The angles in turn are supported at their endsy by means of aring 89, carried by the shell 90 of the reaction chamber. Under thedischarge end of each cone we secure an orifice plate 9| by means of'tapped screws 92 enabling it to be removed lfor replacement by plates 9|having respective orifices 98 of different sizes. The size of the orice98 controls the rate at which the catalyst material will be dischargedfrom the cone.

The arrangement is such that, in tting tube ends to the tubes, it isonly necessary to position their supporting angles 88 below the tubes sothat the tube ends slide easily into the cylindrical portions of thedischarge assembly.

A plurality of angles 94 are supported by a cross member 95 and arepositioned beneath and adjacent respective lines of orices 98. The crossmember 95 is pivotally supported on links 95 and 91 as can readily beseen by reference to Figure 2. The reciprocating rod 55, driven asindicated hereinabove, passes through 2a stuiling box 91 and is adaptedto actuate the gridwork formed by cross members 95 and angles 94. Thereciprocation of the grid alternately moves the angles clear of therespective orices 98 and to a position blocking the same. When the gridis clear of the orifices, catalyst material will ow from the dischargecones 85 to the space 98 beneath the discharge arrangement. From thespace 98 the catalyst material passes by valve 99 into the sealinghopper from which it is discharged past valve |0I. The sealing gas forthe lower hopper is introduced through pipe 58 controlled by controlvalve 69 as described hereinabove.

The slots 88 in the base of the discharge cones are made considerablylarger in total area than the internal cross sectional area of thetubes.

device to the right, as view in Figure 7, is adapted to dump thecatalyst material. As the catalyst material is being dumped, theimperforate portion of the angle |08 moves across the outlet of thedischarge cone 85. The arrangement is a volumetric discharge device inwhich the speed of reciprocation oi' the shaker device will accuratelycontrol the flow of catalyst.

In a test operation, the oil being charged was heated to a transfertemperature of 925 F. and was chargedat this temperature into thecatalyst chamber under a pressure of about 13 pounds per square inch.The fractionating tower. was held at a top temperature of 240 F. and,charging 9020 pounds per hour of 21 A. P. I. charging stock, 1590 poundsper hour of 63.5 A. P. I. gasoline was produced 4388 pounds per hour of27 A. P. I. cycle stock was withdrawn from the bottom of thefractionating tower. 2480 pounds per hour of 7.8 A. P. I. tar bottomswere withdrawn from the bottom of the evaporating tower. About 335pounds per hour of gas was introduced into the gas mains from theseparator.

As shown, the area of the slot is substantially t four times as large asthe internal cross sectional area of the tubes. This enables readyseparation of the cracked vapors from the spent catalyst material to beeffected. The discharge valves 89 and |0| and the catalyst feeding valve18 are operated either by electrical or fluid pressure control mechanismin accordance with a time cycle regulated to introduce the catalyst atdefinite intervals in amounts proportioned according to the rate ofcatalyst flow from the tubes. A level gauge (not shown) 'may be employedin an upper feed compartment. A level gauge may be employed to indicatethe amount of catalyst material in a lower discharge compartment. 'I'hechange in levels of the upper and lower hoppers will serve to indicatethe rate of catalyst flow through the catalyst chamber.

In the form of the discharge portion of the cones shown in Figures 7 and8, the angles |02 are stationary while the angles |08 secured to thecross members 95 are movable by the shaker mechanism. 'I'he angles |08are provided with orices |08 disposed beneath the outlet of eachdischarge cone 85. A pair of longitudinal, downwardly projecting members|05 and |08 form an elongated chamber |01 with the bottom of stationaryangle |02. 'I'he catalyst is adapted to nil the chamber |01. Movement ofthe shaker This gas had a molecular weight of about 23. Burner 21,generating hot gases of combustion for the heating jacket, consumed 69.2pounds per hour of gas. The furnace 8 consumed 374 pounds per hour offuel gas. A pressure oi' 13 pounds per square inch was maintained in theupper sealing hopper 22 and a pressure of 6 pounds per square inch wasmaintained in the` lower sealing hopper 80. It required about 58.2pounds per hour oi' sealing gas to maintain the desired pressure. Thegases of combustion entered the heating jacket at a temperature of about1425 F. and were withdrawn from the heating jacket through duct 80 at atemperature of 1000 F.

'I'he rate of flow of the heating gas through the heating jacket was8300 pounds per hour.

It will be seen that we have accomplished the objects of our invention.We have provided a method of catalytic cracking in which the catalyticmaterial flows concurrently with the flow of the hot vapors to becracked. Concurrent flow enables us to produce maximum yields per passof a premium motor fuel having an increased octane number. Static bodiesof catalyst in contact with reactant vapors are avoided and moreaccurate control over the flow of the catalyst is exercised.

. Side reactions occasioned by the contact of .l hot. freshly crackedhydrocarbons with more active catalyst material are avoided. Smalleramounts of fixed gases are produced. Our apparatus enables us toaccurately control the flow oi' the catalytic material and to govern theamount of catalytic material to be employed, depending on the particulartype of oil to be cracked and the particular type of catalytic materialto be used. Once the operating conditions have been established for aparticular type of crude oil being charged, our process may be runcontinuously without the necessity of shutting the plant to recharge thecatalytic. material.

It will be understood that certain features and sub-combinations are ofutility'and may heemployed without reference to other features andsub-combinations. This is contemplated by and is within the scope of ourclaim. It is further obvious that various changes may bel made indetails within the scope of our claim without departing from the spiritof our invention. It is, therefore, to be understood that our inventionis not to be limited to the specific details shown and described.

Having thus described our invention, we claim: A catalyst chambercomprising in combination a plurality of vertical open end tubespodtioned in said chamber, means for introducing catalyst material tothe upper end of said tubes for passage therethrough, closure platesmounted on n. reciprocable support and positioned below the lower end ofsaid tubes. each of said closure plates having an imperforate sectionand a section having a perforation therein, each of said sections beingadapted to be alternately brouzbt into alignment with the lower end oi'one oi' said

